Using an External Graphics Editor, we can make UV maps for our model.
You can learn step by step how to UV unwrap any model and then how we may UV Map it using any External Graphics Editor.
By exporting UV layout of any 3D model, we can make UV texture for it. And then we can apply that UV texture to the 3D model.
In 3d modelling, UV unwrapping and UV mapping are important for texturing. Almost every 3d model, UV unwrapped and then UV mapped. The process of creating a UV layout is called UV unwrapping.